Fluid pressure operated switches



p 1955 w H. RUFFLE FLUID PRESSURE OPERATED SWITCHES 2 Sheets-Shee 1 Filed June 5, 1951 Sept. 20, 1955 w. H. RUFFLE 2,713,565

FLUID PRESSURE OPERATED SWITCHES Filed June 5, 1951 2 Sheets-Sheet 2 United States Patent 0 FLUID PRESSURE OPERATED SWITCHES William Harry Ruffle, Hove, England, assignor to Speed Development Company Limited, Hove, England Application June 5, 1951, Serial No. 229,907 Claims priority, application Great Britain June 14, 1950 7 Claims. (Cl. Nil-81.5)

This invention relates to fluid pressure operated switches of the type in which the switch is operated in response to changes in fluid pressure applied to a flexible diaphragm disposed within a housing or base structure adapted for the reception of means for connecting it to the source of fluid pressure, and carrying a driver member actuated from the diaphragm and having operative engagement with a contact carrying or operating member. Such a type of switch which embodies many of the features of the present invention is found in Patent 2,571,617.

In the latter mentioned switch there is provided a base structure, a fluid pressure receiving compartment, a fluid pressure inlet to said compartment, an imperforated diaphragm sealed completely around its periphery and disposed across said compartment so that only one side thereof is subjected to the direct impact of the fluid pressure from said inlet, a stud co-axial with the diaphragm and slidable through the base structure, a disc-like head on said stud opposed to but free of said diaphragm so as to be engaged by the diaphragm when the latter is deformed by the fluid pressure so as to urge the stud in the direction of deformation of the diaphragm, a very shallow compartment accommodating said disc-like head with a very narrow clearance from the periphery of said head opening into and concentric with and very narrowly axially spaced from the said fluid pressure receiving compartment so that the said head and the ambient part of the wall of the fluid pressure receiving compartment only permit of a very limited deformation of the diaphragm irrespective of the head of fluid pressure, an abutment on said stud which rests upon the base structure to relieve the diaphragm of pressure via the stud and its head when the diaphragm is not pressing against said head, a lever operated in one direction and engaged by said stud, contacts brought into and out of engagement by the movement of said lever, spring means yieldingly opposing the displacement of the lever by the action of the fluid pressure, and means neutralising the influence of the weight of said switch actuating member against the switch lever. The said neutralising means is applied as a permanent load in the form of a counterweight, but it is found that in some fields of use the switch must respond accurately to a predetermined differential of pressure in which the condition obtaining regarding the position of the contacts is required to be kept between two pressure levels. In the case of a pressure controller for controlling the pressure in a cabin on an aircraft, for example, it may be important that the pressure be maintained between reliable predetermined limits, e. g., to allow for a maintenance of the switch in the on or off position, according to which is appropriate, when actuated in the manner which will avoid fluctuations with pressure variations of only a small p. s. i. It is necessary, therefore, to introduce a definite controlled artificial differential into the switch as distinct from merely relying upon a counterbalance weight in order to obtain the result the pressure equipment requires, e. g. to prevent hunting of a motor 2,718,555 Patented Sept. 20, 1955 ice brought in by the switch and which would occur should the switch be set at a fixed p. s. i. level.

Further, in certain other, or in the foregoing fields of use, it is necessary for the switch to respond accurately to the predetermined pressure or change in pressure and to be capable of withstanding very high pressures without injuring the diaphragm whilst at the same time affording a very highly sensitive form of response in the contact actuating means, and also for the switch to be set to respond to a predetermined one of a wide range of pressures. Also, it is desirable in many fields, e. g. on air craft, for a switch of the class in question to be capable of responding in the predetermined manner irrespective of the attitude or change in physical position of the switch as a whole, and still further to eliminate entirely fluctuation in the operation of the switch whether in the on or off position, whereby there is a positive prompt response of the switch to the predetermined pressure or change in pressure and an equally positive retention of the switch in the desired position. That is to say the present invention contemplates a very sensitive switch as in Patent 2,571,617 in which whatever the fluid pressure load the switch will respond accurately at the predetermined point in the load but which, when actuated, will remain set despite thereafter fluctuations of a few pounds per square inch in the fluid pressure operating the switch.

According to the present invention a fluid pressure actuated electrical switch incorporates the aforesaid arrangement of very sensitive flexible diaphragm actuated means of the switch shown in Patent 2,571,617 for actuating a switch lever, but instead of using a counterbalance weight with the lever there is provided an electro-magnet and the switch lever is the armature, the switch contacts when engaged connecting the electro-magnet in circuit to energise it and the said lever assuming a position when in the contact closed condition of the switch which is the position in which it is held by the energised electro magnet without adding to the load on the diaphragm, the switch arm being urged off the energised electro-magn'et by the load thereon due to the predetermined change in fluid pressure on the diaphragm.

The present invention may also be said to be characterised by the provision with the switch of an electro-magnet which is energised when the switch is in a predetermined set condition, and the combination with the electromagnet, of an armature formed as part of, or carried by, a displaceable switch member or actuating member, so as to give a predetermined restraint to the movement of the armature, and, therefore, to the said actuating switch member, for a part of the cycle of operation of the switch, and spring means yieldingly opposing the operation of the switch by fluid pressure and co-operating with the electro-magnet to assist the restraining load of the electro-magnet for predetermining the fluid pressure load which will actuate the switch to the on or off condition according to the desired mode of the operation of the switch.

In order that the invention may be clearly understood and readily carried into effect drawings are appended hereto illustrating embodiments thereof, and wherein,

Figure 1 is a sectional elevation on the line I-I of Figure 3.

Figure 2 is a section on the line IIII of Figure 1.

Figure 3 is a section on the line III-II1 of Figure 1.

Figure 4 is a plan view of the switch with the cover cap removed.

Figure 5 is a diagramof the circuit of the switch illustrated in the foregoing figures, and

Figure 6 is a broken detail sectional elevation, view showing a reverse arrangement of the switch contacts.

Referring to the drawings, the switch has a body or base portion constituted by two stout discs 1 and 2' abutted together to grip between them an imperforated flexible diaphragm 3, the lower one of these discs having a concentric boss 1 to form an annular ledge 1a forming an abutment for an annular locking ring 4 threaded on to the lower part of the periphery of a cylindrical housing 5. The said bossed 1 portion of the lower disc 1 has a central bore 6 for connection to the source of fluid pressure and this communicates with a shallow cylindrical compartment 7 exposing the concentric central portion of the diaphragm 3, the upper disc 2 also having a shallow cylindrical compartment 8 in which nests as a very slight loose fit a disc 9 comprising the head of a stud 10 slidable through a concentric centre bore 11 of the upper disc 2, the axial dimension of the compartment 8 being such that the displacement of the stud 10 axially is very slight in order to minimise as much as possible deformation of the diaphragm. In this connection, the periphery of the disc 9 has only the said very slight clearance from the cylindrical wall of the compartment 8 to obviate deformation of the diaphragm over the periphery of the disc. All of these features are found in the switch described in Patent No. 2,571,617.

The end of the stud 10 which passes above the upper disc 2 abuts against a single ball bearing element 12 seated within the flared lower end of a hole 14 formed approximately midway between the end of a substantially horizontal lever arm 15 in the form of a metal bar stepped as at 15' at one end where it operates between a pair of contact carrying leaf springs 16 and 17 and is fitted with a contact operating stud 18 to engage the upper one 16 of the leaf springs to separate the contacts 16 and 17 carried by the leaf springs 16 and 17 respectively to actuate the switch to the off position when the stud 10 is urged by the diaphragm 3 upwardly due to the fluid pressure reaching a predetermined maximum. This can be regarded as a normal condition when a warning for a drop in pressure is desired. Between the said ball 12 engaged in the lever arm 15 and the end remote from the contact actuating end, a transverse pivot pin 19 is passed and engaged in the depending side lugs 20 of a shallow inverted rectangular U-shaped bridge 20 secured to the disc 2 by screws 20a; this pivot pin constitutes the fulcrum of the lever arm 15, and the end of this arm adjacent the fulcrum constitutes a soft iron armature 15a disposed opposite the lower part of an electro-magnet 21 which can be of the simple twin coil type or horseshoe type, the top of the housing 5 having fitted centrally therein a three-pin plug 22 from the socket portion of which leads a, b and c are taken for the contacts 16 and 17 and the electro-magnet respectively.

A pair of vertical posts 23 secured in the top disc 2 of the base structure carrying a bridge member 24 between which and the said lever arm is interposed an adjustable coiled compression spring 25, the ends of this spring being seated in two abutment discs 26 and 27 secured to the bridge member and the lever arm by screws 28, this bridge also having secured to it by screws 29 a horizontal insulating plate 30 carrying a limiting resistor 31 connected, as shown in Figure 5, in series with the electro-magnet 21 so that the electro-magnet 21 and resistor 31 are connected across one of the leads 0 of a D.-C. supply and a lead b passing from one of the other terminals of the three-pin plug connector 22 and the switch contact 17, the other lead a from the D. C. supply being connected to the other switch contact 16, and the lead b including in its connection to the source a load L such as e. g. a warning lamp.

The two switch contact carrying leaf springs are supported at one end by insulated distance-pieces 32 on a post 33 secured to the base of the switch, and the said lever arm at the stepped end carrying the stud 18 operating between these two leaf springs. In the case of a break type switch as shown an insulated pillar 37 is fixed to the disc 2 to restrict downward movement of the spring 17, and a variant of this insulated stud is used to restrict downward movement of the spring 16 in a make type switch.

The electro-magnet 21 is supported from an insulating bridge 34 secured to the base disc 2 by posts 35, screws 36 securing the electro-magnet to the bridge 34.

To prevent straining of the diaphragm by the load of the spring 25, the stud 10 has a flange 10 at its upper end to serve as a stop against the disc 2: a perforated disc 38 protects the diaphragm against excessive deformation due to suction.

By means of the present invention the electro-magnet 21 will be energised when the contacts of the two leaf spring members are engaged and the desired circuit, e. g. a warning signal circuit, is closed.

In the embodiment shown in Figures 1-4 the warning circuit is closed when fluid pressure urging the stud 10 upwards drops below the load of the spring 25, the closing of this circuit then bringing in the electro-magnet 21 which thereby positively holds the lever arm 15 in the circuit-closed position. Hence in order to restore the switch to the normal or circuit-open position there must be a quite definite positive fluid pressure on the diaphragm 3 to overcome the load of the spring 25 and the effective effort of the electro-magnet 21. By this means are obviated fluctuations in pressure close to the predetermined minimum fluid pressure range when the warning or other load circuit is closed, whereby intermittent making and breaking of the circuit is avoided.

By reversing the relationship of the electro-magnet 21 and the said armature lever arm 15, and also the relationship of the arm 15 with contact leaf springs 15 and 16, as shown in Figure 6, the electro-magnet 21 can be maintained de-energised until a predetermined rise in fluid pressure acting on the diaphragm 3 is reached to give a warning or operate a motor controller, pressurerelief valve or other suitable load.

By bringing into circuit the electro-magnet during the desired stage it will be impossible for the lever arm to be displaced until the fluid pressure overcomes the influence of the spring and electromagnet in one arrangement, or in the other arrangement until the fluid pressure drops to a predetermined minimum. Hence, as the restraint of the energised electro-magnet 21 is added to the influence of the spring 25 for only part of the cycle of operation, adjustment of the effective energy of the electro-magnet will give any desired added differential at the pressure levels of operation and resetting of the switch.

The adjustment of the spring 25 may be varied by raising or lowering the plate 24, and the differential control may be varied by raising or lowering the platform 34 and also by varying the value of the resistance 31, e. g. by pre-selecting a resistor 31 of the desired value.

I claim:

1. A fluid pressure operated switch sensitive to and adapted to respond to a very slight change in a predetermined fluid pressure and to be maintained in the on or off position during the continuance of said change in fluid pressure, comprising a base structure, a fluid pressure receiving compartment, a fluid pressure inlet to said compartment, an imperforated diaphragm sealed completely around its periphery and disposed across said compartment so that only one side thereof is subjected to the direct impact of the fluid pressure from said inlet, a stud co-axial with the diaphragm and slidable through the base structure, a disc-like head on said stud opposed to but free of said diaphragm so as to be engaged by the diaphragm when the latter is deformed by the fluid pressure so as to urge the stud in the direction of deformation of the diaphragm, a very shallow compartment accommodating said disc-like head with a very narrow clearance from the periphery of said head opening into and concentric with and very narrowly axially spaced from the said fluid pressure receiving compartment so that the said head and the ambient part of the wall pf the fluid pressure receiving compartment only permit of a very limited deformation of the diaphragm, irrespective of the head of fluid pressure, means to relieve the diaphragm of pressure via the stud and its head when the diaphragm is not pressing against said head, a lever operated via said stud in one direction by the fluid pressure on the diaphragm, contacts brought into and out of engagement by the movement of said lever, spring means yieldingly opposing the displacement of the lever by the action of the fluid pressure, and an electro-magnet the armature of which is constituted by said lever and so related to the lever that when the said contacts are engaged the lever is in the position in which it is held by the electro-magnet when the electro-magnet is energised, leads to connect the electro-magnet to a source of electrical energy and connections to said leads from said contactsso that the electro-magnet is only energised when the contacts are'cl'osed and the opening of the contacts and separation of the lever from the electro-rnagnet is made by the overcoming of the load which previously actuated the-switch.

2., A, fluid pressure operated switch comprising a base structure, a fluid pressure receiving compartment, 21 fluid pressure inlet to said compartment, an imperforated diaphragm sealed completely around its periphery and disposed across said compartment sothat only one side thereof is subjected to the direct impact of the fluid pres sure from said inlet, a stud co-axial with the diaphragm and slidable through the base structure, a disc-like head on said stud opposed to but free of said diaphragm so as to be engaged by the diaphragm when the latter is deformed by the fluid pressure so as to urge the stud in the direction of deformation of the diaphragm, a very shalloweompartment accommodating said disc-like head with a very narrow clearance from the periphery of said head opening into and concentric with and very narrowly axially spaced from the said fluid pressure receiving compartment so that the said head and the ambient part of the wall of the fluid pressure receiving compartment only permit of a very limited deformation of the diaphragm irrespective of the head of fluid pressure, an abutment on said stud which rests upon the base structure to relieve the diaphragm of pressure via the stud and its head when the diaphragm is not pressing against said head, an electro-magnet, a lever comprising the armature of said electro-magnet operated in one direction and engaged by said stud, a pair of opposed contacts in series connection with the winding of the electro-magnet and made and broken by the movement of said lever to effect energising and de-energising respectively of said electro-magnet, spring means yieldingly opposing the displacement of the lever by the action of the fluid pressure and means to adjust the effective load of said spring upon the lever to overcome the force of the electro-rnagnet at a predetermined change in fluid pressure.

3. A fluid pressure operated switch comprising a base structure, a fluid pressure receiving compartment, a fluid pressure inlet to said compartment, an imperforated diaphragm sealed completely around its periphery and disposed across said compartment so that only one side thereof is subjected to the direct impact of the fluid pressure from said inlet, a stud co-axial with the diaphragm and slidable through the base structure, a disclike head on said stud opposed to but free of said diaphragm so as to be engaged by the diaphragm when the latter is deformed by the fluid pressure so as to urge to stud in the direction of deformation of the diaphragm, a very shallow compartment accommodating said disclike head with a very narrow clearance from the periphery of said head opening into and concentric with and very narrowly axially spaced from the said fluid pressure receiving compartment so that the said head and the ambient part of the wall of the fluid pressure receiving compartment only permit of a very limited deformation of the diaphragm irrespective of the head of fluid pressure, an abutment on said stud which rests upon the base structure to relieve the diaphragm of pressure via the stud and its head when the diaphragm is not pressing against said head, an electro-magnet, a lever arm operated in one direction and engaged by said stud and one end of which lever arm is opposed to and forms the armature of said electro-magnet, a fulcrum pivot for the lever arm between the electro-magnet and the stud, a pair of opposed contacts in series connection with the winding of said electro-magnet, a leaf spring carrying one of the contacts and urging the contacts into engagement and pressing against the other end of said lever, and spring means loading said lever arm in yielding opposition to the fluid pressure.

4. A fluid pressure operated switch comprising a base structure, a fluid pressure receiving compartment, a fluid pressure inlet to said compartment, an imperforated diaphragm sealed completely around its periphery and disposed across said compartment so that only one side thereof is subjected to the direct impact of the fluid pressure from said inlet, a stud co-axial-with the diaphragm and slidable through the base structure, a disc-like headon said stud opposed to but free of said diaphragm so as to be engaged by the diaphragm when the latter is deformed by the fluid pressure so as to urge the stud in the direction of deformation of the diaphragm, a very shallow compartment accommodating said disc-like head With a very narrow clearance from the periphery of said head opening into and concentric with and very narrowly axially spaced from the said fluid pressure receiving compartment so that the said head and the ambient part of the wall of the fluid pressure receiving compartment only permit of a very limited deformation of the. diaphragm irrespective of the head of fluid pressure, an abutment on said stud which rests upon the base structure to relieve the diaphragm of pressure via the stud and its head when the diaphragm is not pressing against said head, a lever arm a fulcrum for said lever at one end of the lever, an electro-magnet opposed to said lever arm between the ends of the lever, said lever arm comprising the armature of the electro-magnet, a pair of opposed contacts in series connection with the Winding of said electro-magnet, a leaf spring carrying one of the said contacts and urging such contact away from the other and pressing against the end of the lever remote from the fulcrum, and spring means loading said lever in yielding opposition to the fluid pressure.

5. A fluid pressure operated switch comprising a base structure, a fluid pressure receiving compartment, a fluid pressure inlet to said compartment, an imperforated diaphragm sealed completely around its periphery and disposed across said compartment so that only one side thereof is subjected to the direct impact of the fluid pressure from said inlet, a stud co-aXial with the diaphragm and slidable through the base structure, a disclike head on said stud opposed to but free of said diaphragm so as to be engaged by the diaphragm when the latter is deformed by the fluid pressure so as to urge the stud in the direction of deformation of the diaphragm, a very shallow compartment accommodating said disclike head with a very narrow clearance from the periphery of said head opening into and concentric with and very narrowly axially spaced from the said fluid pressure receiving compartment so that the said head and the ambient part of the wall of the fluid pressure receiving compartment only permit of a very limited deformation of the diaphragm irrespective of the head of fluid pressure, an abutment on said stud which rests upon the base structure to relieve the diaphragm of pressure via the stud and its head when the diaphragm is not pressing against said head, an electro-magnet, a lever comprising the armature of said electro-magnet operated in one direction and engaged by said stud, a pair of opposed contacts in series connection with the winding of the electro-magnet and made and broken by the movement of said lever to effect energising and de-energising respectively of said electro-magnet, spring means yieldingly opposing the displacement of the lever by the action of the fluid pressure, and means to adjust the gap between the electro-magnet and the said lever.

6. A fluid pressure operated switch comprising a base structure, a fluid pressure receiving compartment, a fluid pressure inlet to said compartment, an imperforated diaphragm sealed completely around its periphery and disposed across said compartment so that only one side thereof is subjected to the direct impact of the fluid pressure from said inlet, a stud co-axial with the diaphragm and slidable through the base structure, a disc-like head on said stud opposed to but free of said diaphragm so as to be engaged by the diaphragm when the latter is deformed by the fluid pressure so as to urge the stud in the direction of deformation of the diaphragm, a very shallow compartment accommodating said disc-like head with a very narrow clearance from the periphery of said head opening into and concentric with and very narrowly axially spaced from the said fluid pressure receiving compartment so that the said head and the ambient part of the wall of the fluid pressure receiving compartment only permit of a very limited deformation of the diaphragm irrespective of the head of fluid pressure, an abutment on said stud which rests upon the base structure to relieve the diaphragm of pressure via the stud and its head when the diaphragm is not pressing against said head, an electro-magnet, a lever arm operated in one direction and engaged by said stud and one end of which lever arm is opposed to and forms the armature of said electromagnet, a fulcrum pivot for the lever arm between the electro-magnet and the stud, a pair of opposed contacts in series connection with the winding of said electromagnet, a leaf spring carrying one of the contacts and urging the contacts into engagement and pressing against the other end of said lever, a coiled compression spring, and an adjustable stop for one end of said spring, said spring being interposed under compression between said stop and said lever arm and operating in opposition to the fluid pressure.

7. A fluid pressure operated switch comprising a base structure, a fluid pressure receiving compartment, a fluid pressure inlet to said compartment, an irnperforated diaphragm sealed completely around its periphery and disposed across said compartment so that only one side thereof is subjected to the direct impact of the fluid pressure from said inlet, a stud co-axial with the diaphragm and slidable through the base structure, a disclike head on said stud opposed to but free of said diaphragm so as to be engaged by the diaphragm when the latter is deformed by the fluid pressure so as to urge the stud in the direction of deformation of the diaphragm, a very shallow compartment accommodating said disclike head with a very narrow clearance from the periphery of said head opening into and concentric with and very narrowly axially spaced from the said fluid pressure receiving compartment so that the said head and the ambient part of the wall of the fluid pressure receiving compartment only permit of a very limited deformation of the diaphragm irrespective of the head of fluid pressure, an abutment on said stud which rests upon the base structure to relieve the diaphragm of pressure via the stud and its head when the diaphragm is not pressing against the said head, an electro-magnet, a lever arm operated in one direction and engaged by said stud and one end of which lever arm is opposed to and forms the armature of said electro-magnet, a fulcrum pivot for the lever arm between the electro-magnet and the stud, a pair of opposed contacts in series connection with the winding of said electro-magnet, a leaf spring carrying one of the contacts and urging the contacts into engagement and pressing against the other end of said lever, a coiled compression spring, and an adjustable stop for one end of said spring, said spring being interposed under compression between said stop and said lever arm and operating in opposition to the fluid pressure.

References Cited in the file of this patent UNITED STATES PATENTS 1,214,920 Holland Feb. 6, 1917 1,827,103 Penn Oct. 13, 1931 2,310,138 Whittaker Feb. 2, 1943 2,571,617 Ruflie Oct. 16, 1951 

